Isolated rabbit gastric glands are made permeable to solutes such as ATP but retain H ion transport capability in the presence of this substrate. Using this model, the cellular site of action of 2nd messenger will be investigated, as will the determinants of the morphological transformation of the parietal cell, the exact energy source of acid secretion, the role of Na ion and K ion with respect to the luminal and cytoplasmic face of the secretory canaliculus, as well as electrogenicity of H ion secretion. The intact secretory canaliculus will be isolated and its structural and functional properties determined.